Species Selective Predation on Juvenile Pink (Oncorhynchus gorbuscha) and Chum Salmon (O. keta) by Coho Salmon (O. kisutch)

Hargreaves, N. Brent; LeBrasseur, R. J.

doi:10.1139/f85-085

Cited by 30 publications

(36 citation statements)

References 8 publications

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“…Emergent fry were examined for gross and cellular abnormalities, then cultured for 5 mo in clean water to measure delayed impacts on growth. Evaluated after exposure ended, growth was identified as an integrator of intermediateand long-term delayed response because failure to grow rapidly reduces marine survival (Parker 1971, Hargreaves & LeBrasseur 1985. Our results are extended by responses to similar oil exposures in several previous brood years, including delayed reduction of growth and long-term marine survival (Marty et al 1997, Heintz et al 1999.…”

Section: Introductionsupporting

confidence: 55%

Cytochrome P4501A induction in oil-exposed pink salmon Oncorhynchus gorbuscha embryos predicts reduced survival potential

Carls¹,

Heintz²,

Marty³

et al. 2005

Mar. Ecol. Prog. Ser.

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Cytochrome P4501A (CYP1A) induction in pink salmon Oncorhynchus gorbuscha embryos exposed to crude oil is linked to adverse effects at cellular, organism and population levels, and can be used to predict these responses. When combined with the results of an experiment designed to examine CYP1A induction during embryonic stages and growth after emergence, results from a series of experiments spanning 4 other brood years demonstrated that CYP1A induction is related to a variety of lethal and sublethal effects, including poorer marine survival, reduced growth and abnormalities. The lowest observed effective concentration of total polynuclear aromatic hydrocarbons (TPAH) in water that caused significant physiological responses, including reduced size 6 mo after exposure ended (< 0.94 µg l -1 ), was less than the lowest concentration that caused significant CYP1A induction (< 3.7 µg l -1 ). Thus, CYP1A induction is not only a biomarker, it can be considered a bioindicator; induction in early life stages implies long-term negative consequences for the individual and the population.

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Section: Introductionsupporting

confidence: 55%

Cytochrome P4501A induction in oil-exposed pink salmon Oncorhynchus gorbuscha embryos predicts reduced survival potential

Carls¹,

Heintz²,

Marty³

et al. 2005

Mar. Ecol. Prog. Ser.

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“…Considering the 24-hour experiments only, predators consumed an average of 1.88 prey each. This was consistent with observations by Hargreaves and LeBrasseur (1985) who found that coho consumed an average of 2-3 pink or chum salmon per day at the beginning of their experiments (as experiments progressed and coho grew, this increased to ;6 prey per day) and observations from Krkošek et al (2011), who estimated that coho consumed approximately one prey per day in their group predation experiments. Based on this information, we assumed that the average coho satiates at two prey per day and set T h ¼ 0.5 days.…”

Section: Relating Results To Functional Response Modelsupporting

confidence: 89%

“…Our results clearly indicate that coho predators preferentially consume pink salmon over chum salmon, consistent with a previous study reporting species-selective predation by coho salmon (Hargreaves and LeBrasseur 1985). In the absence of sea louse infestations, the predation mortality of pink salmon was significantly higher than that of chum salmon (Fig.…”

Section: Discussionsupporting

confidence: 92%

“…Attack rates may differ among prey species, in which case the predator is said to have a preference for the species with the higher attack rate (Chesson 1983). Due to previous evidence of selective predation on pink salmon (Hargreaves and LeBrasseur 1985), we chose the attack rate on pink salmon to be greater than the attack rate on chum salmon. Handling time may also differ between prey species, but here we assume that it is the same for both prey species because juvenile pink and chum salmon are morphologically and behaviorally similar.…”

Section: The Functional Responsementioning

confidence: 99%

“…Juvenile coho salmon (O. kisutch) spend a year in freshwater before migrating to sea and are primary predators of juvenile pink and chum salmon (Parker 1969). Previous experimental work found that coho salmon predators preferentially consume pink salmon over chum salmon (Hargreaves and LeBrasseur 1985). A mathematical model tailored to the system suggested that if this preference were amplified by infestations, then sea lice may reduce predation on chum salmon (Peacock et al 2014), offsetting the direct effects of parasitism and dampening the population-level impact.…”

Section: Introductionmentioning

confidence: 97%

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Parasitism and food web dynamics of juvenile Pacific salmon

et al. 2015

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Abstract. There is an increasing realization of the diverse mechanisms by which parasites and pathogens influence the dynamics of host populations and communities. In multi-host systems, parasites may mediate food web dynamics with unexpected outcomes for host populations. Models have been used to explore the potential consequences of interactions between hosts, parasites and predators, but connections between theory and data are rare. Here, we consider sea louse parasites (Lepeophtheirus salmonis), which directly increase mortality of juvenile salmon hosts (Oncorhynchus spp.). We use mathematical models and field-based experiments to investigate how the indirect effects of parasitism via predation influence mortality of sympatric juvenile chum salmon (O. keta) and pink salmon (O. gorbuscha). Our experiments show that coho salmon predators (O. kisutch) selectively prey on pink salmon and on parasitized prey. Preference for pink salmon increased slightly when prey were parasitized by sea lice, although there was considerable uncertainty regarding this result. Despite this uncertainty, we show that even the small increase in preference that we observed may be biologically significant. We calculate a critical threshold of pink salmon abundance above which chum salmon may experience a parasitemediated release from predation as predation shifts towards preferred prey species. This work highlights the importance of considering community interactions, such as predation, when assessing the risk that emerging parasites and pathogens pose to wildlife populations.

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Spatiotemporal Variation and Size‐Selective Predation on Hatchery‐ and Wild‐Born Juvenile Chum Salmon at Marine Entry by Nearshore Fishes in Southeast Alaska

Duncan

Beaudreau

2019

Mar Coast Fish

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Juvenile Pacific salmon Oncorhynchus spp. experience high mortality at marine entry, yet our quantitative understanding of predation during this critical period is limited. We evaluated spatial, temporal, and size‐based patterns of predation on hatchery‐ and wild‐born juvenile Chum Salmon O. keta by two abundant predators in Southeast Alaska estuaries: the Pacific Staghorn Sculpin Leptocottus armatus and Dolly Varden Salvelinus malma. For the predators we sampled, Chum Salmon comprised 4.5% of the diet by weight for Pacific Staghorn Sculpin (n = 937) and 19.6% of the diet by weight for Dolly Varden (n = 448), with 88% of the individual Chum Salmon consumed originating from hatcheries. Variation in occurrence of Chum Salmon in diets was driven by date, site, and local Chum Salmon density. The quantity of Chum Salmon consumed by Pacific Staghorn Sculpin varied with predator length, Chum Salmon density, and the proportion of hatchery fish present; however, date was the only important predictor for Dolly Varden. The mean length of Chum Salmon in the diets of both predators was significantly shorter than that of concurrent hatchery releases or seine catches, suggesting size‐selective predation on smaller individuals. This pattern indicates that hatchery strategies of releasing larger individuals may reduce the initial vulnerability of hatchery salmon to estuarine predators.

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Species Selective Predation on Juvenile Pink (Oncorhynchus gorbuscha) and Chum Salmon (O. keta) by Coho Salmon (O. kisutch)

Cited by 30 publications

References 8 publications

Cytochrome P4501A induction in oil-exposed pink salmon Oncorhynchus gorbuscha embryos predicts reduced survival potential

Cytochrome P4501A induction in oil-exposed pink salmon Oncorhynchus gorbuscha embryos predicts reduced survival potential

Parasitism and food web dynamics of juvenile Pacific salmon

Spatiotemporal Variation and Size‐Selective Predation on Hatchery‐ and Wild‐Born Juvenile Chum Salmon at Marine Entry by Nearshore Fishes in Southeast Alaska

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